The field of the invention generally relates to infrared control systems that implement repeater or extension systems, and more specifically to components thereof that are interference resistant.
Infrared (“IR”) Control Systems
IR control systems can allow a user to control many conventional audio and video components, such as televisions and stereo equipment as well as more recently developed technologies such as Digital Versatile Disc players (DVD players), and electronic video recorders. Increasingly, use of such systems has expanded to control home and office fixtures such as lighting; mechanical systems such as heating, ventilation and air conditioning; and appliances such as automated coffee machines and dishwashers.
A wide variety of IR remote controls are typically used to control such IR control systems. Such IR remote controls are generally product or component specific depending upon the manufacturer. Traditional narrow-band tuned IR remote control systems employ a handheld remote control that includes a transmitter and a stationary receiver.
The transmitter typically includes a modulating circuit and a light emitting diode. The modulating circuit determines the frequency at which the light emitted from the diode is modulated. The light emitting diode emits short pulses of IR light when the diode is energized, and the wavelength of the IR light is based on the physical properties of the light emitting diode. These short pulses of IR light are encoded with data.
The receiver typically includes a detector that detects incoming IR light signals emitted from the light emitting diode, and an amplifier that is “tuned” or configured to respond to the modulation frequency of the light emitted from the light emitting diode. The amplifier amplifies the output of the detector, which converts the incoming modulated IR light to a corresponding modulated electrical signal, before transmitting that output signal to control circuitry. The control circuitry then demodulates the data stream and controls operation of the device.
Manufacturers typically employ IR control systems that are tuned on a product-by-product basis to a chosen narrow-band frequency. In most cases, the IR light is modulated using a carrier frequency of 38 KHz, 56 KHz, or 455 KHz. There are also a variety of remote control code protocols, and most protocols use different spacing and timings of carrier-modulated infrared signal bursts to encode commands and data. As such, a tremendous amount of variation exists among control systems.
Extension or Repeater Systems
One problem with conventional control systems resides in the inability to control a component outside the line-of-sight or beyond the transmission range of the component's IR receiver, for example, when the component is in another room.
To address this problem, IR extension or repeater systems, such as that disclosed in U.S. Pat. No. 4,509,211 to Michael S. Robbins, which is hereby incorporated by reference, have been developed. IR extension or repeater systems can allow the user to control one or more various components by providing a remote link to the component even though the component is remotely located or outside the line-of-sight or range of the transmitter. IR extension or repeater systems ideally output the same coded signal received by the system. A typical IR extension or repeater system generally comprises a receiver that can detect and amplify the IR signal, and a transmitter that “repeats” or retransmits the signal, for example, into another room. As such, the IR extension or repeater system “extends” or “repeats” the IR signal.
Interference and Plasma Displays
Infrared (IR) “noise” can interfere with a signal from the remote control. Traditional sources of IR noise include ambient lighting, such as sunlight, or artificial light sources, such as compact fluorescent lamps. These sources have been recognized in the art for some time, and solutions have been developed to address noise from these sources.
Recently, however, development of new technologies has created new sources of IR interference or “noise.” Plasma displays and Liquid Crystal Displays (LCDs) for television are two of the new IR noise sources that have recently hindered the performance of IR extension or repeater systems. Plasma/LCD displays continuously emit significant amounts of IR radiation, and are often in close proximity to extension or repeater systems. Noise generated by plasma/LCD sources or “plasma/LCD noise” is similar to bursts of carrier-based IR signals emitted by the transmitter of a remote control. In many cases, this noise closely resembles a valid remote signal making it difficult for the IR receiver to reject noise generated by plasma sources. As such, IR receivers can pass such noise as it does valid remote signals whenever direct or reflected signals from a plasma display are received.
In addition, when plasma/LCD noise and a remote control signal are simultaneously received by a component, the component may not properly decipher the signal since the presence of the plasma noise can disrupt decoding of the command signal, and the component to be controlled is unable to recognize the remote command that corresponds to that signal. As a result, the component will fail to respond to the coded transmission, which prevents the component from being controlled as requested by the user.
Accordingly, there is a need to provide an improved extension or repeater systems that reduces or eliminates one or more of the problems set forth above. There is also a need for interference resistant extension or repeater systems that are operable in the presence of IR noise or interference.